Effect of Tb3+ concentration on Sm3+doped leadfluoro-borophosphate glasses for WLED applications

Abstract A new series of Sm3+/Tb3 co-doped leadfluoro-borophosphate glasses with the composition 50B2O3 + (19.5 − x)P2O5 + 10Li2O + 10ZnF2 + 10PbO + 0.5Sm2O3 + xTb2O3 (where x = 0, 0.05, 0.1, 0.25, 0.5, 1 and 2 in wt%) have been prepared following the melt quenching technique. The presence of fundamental vibrational groups such as BO3, BO4 and PO4 were explored through the FTIR and Raman spectral measurements. The nephelauxetic effect on the absorption transitions have been used to elucidate the bonding nature of the Sm3+ ions with the surrounding ligands thus reveal the predominant ionic nature. Effect of Tb3+ ions on the symmetry of the ligand field around the Sm3+ ions have been predicted using asymmetric intensity ratio values. It is observed that asymmetry around the Sm3+ ion increases with Tb3+ ion concentration upto 1 wt% due to the chaos of both the rare earth ions and after that Tb3+ ion concentration dominates thus in-turn creates lower asymmetrical environment. Luminescence quenching effect due to the presence of RE3+ ions concentration has never seen upto almost 2.5 wt% (for both RE ions) hence the present host possess the capability to incorporate more number of RE ions. The decay profile of the Tb3+ ion (5D4) is found tobe single exponential and Sm3+ ion (4G5/2) is found to be non-exponential nature. The decreasing trend in the experimental lifetime value of the Tb3+ ions confirms the energy transfer process takes place from Tb3+ ions to Sm3+ ions and the interaction takes place between Tb3+ and Sm3+ ions is of dipole-dipole nature and the same is analyzed using IH model. The energy transfer efficiency is found to increase from 47% to 54% with Tb3+ ion concentration. The CIE color chromaticity coordinates have been calculated to identify the characteristic emission of the prepared glasses and the correlated color temperature, color purity were also determined. All these results suggest that, BPLS0.5T glass is a potential candidate for warm white light applications with minimal blue hazards.